Tanis said:
When you push left, the camera should go left.
When you push right, the camera should go right.
So...
When you push up, the camera should go up.
When you push down, the camera should go down.
Never got people who could stand the controls going the wrong way.
While the controller/joystick is held parallel to the ground (a very common playing position) pressing "up" on the joystick is not moving upward in space; it's moving
forward. And, as so many have pointed out, from a first person perspective, moving forward without moving entirely is naturally tilting
down. A simple experiment proves this: while sitting upright, move your head forward until you can't anymore. Eventually, unless you're trying to be clever (in which case, you can still move your head forward, so keep moving), you will pivot and look toward the ground. It works the same in reverse, the more backward you move your head, the higher-up your gaze. It's not "wrong", it's science.
Aside: I suspect there is a correlation between playing position and inversion preference. As someone who prefers non-inverted controls, do you (or whomever) hold the controller flush to the ground or to your face?
Moving on: I should point out again, this is relevant primarily with the first-person perspective and only using a joystick. Mouse controls, for example, work differently because mice slide rather than pivot. Similarly, isometric perspectives break this convention, as the world is sliding around in two dimensions rather than pivoting in three. Third-person controls can go either way, depending on the freedom of movement and implementation of the camera rig.
Now, to make things really weird:
On the one hand,
moving the camera upward while locked onto a character/avatar naturally changes the perspective downward.
On the other hand,
tilting the camera upward, by definition, changes its perspective upward.
On yet another hand, because 3D space is weird like that,
flying the camera up without being locked on a target changes only its elevation without tilting upward or downward, OR,
On the same yet slightly different hand (see what I mean?),
sliding the camera forward causes no change in tilt or elevation, creating a zoom-in effect.
All of these and more can - and logically
should - be bound to the "up" button/direction. That's not even talking about other directions and dual stick controls (which have similar translation issues).
Inverted X, however, makes no sense to me in any perspective. I assume it's supposed to be for people who are left-handed, somehow, or suffer from dyslexia or similar conditions. I don't know anyone that plays fully inverted, so I can't and won't speak to it.